1. Field
Example embodiments relate to substrate structures and methods of manufacturing the same, and particularly, to substrate structures including nitride semiconductor thin films grown with a reduced dislocation density, and in which cracks are reduced and/or prevented, and methods of manufacturing the substrate structures.
2. Description of the Related Art
Light emitting diodes (LEDs) may be divided into GaN-based LEDs and white LEDs that are manufactured based on phosphors. The GaN-based LEDs are predominantly manufactured on 2-inch sapphire substrates. A method of manufacturing GaN-based LEDs on 4-inch substrates is still at an initial stage. In contrast, most semiconductor based devices may be manufactured on silicon wafers of 12 inches (300 mm) or greater in high volume production.
In order to increase LED wafer yield and to reduce LED manufacturing costs, large diameter substrates may be required. However, the use of larger diameter substrates for LED manufacture is gated by material compatibility issues. For example, when semiconductor layers are grown on large diameter sapphire substrates, the substrates may bend at high temperature due to the low thermal conductivity of sapphire. Thus it is difficult to maintain uniform thin film characteristics.
In order to reduce or eliminate substrate bending, a method of epitaxially growing a GaN LED on a silicon substrate has been suggested. Silicon substrates have higher thermal conductivity than sapphire substrates. Thus, the degree of bending of a silicon substrate which is exposed to a high GaN thin film growth temperature may be reduced and an 8-inch substrate having uniform thin film characteristics may be observed. Thus, if a high quality LED thin film may be grown in a GaN LED-on-silicon structure, the limitations of the sapphire substrate may be overcome and manufacturing costs may be reduced.
However, the use of silicon substrates poses different issues. Due to large lattice mismatch and inconformity of thermal expansion coefficients, LED semiconductor thin films grown on silicon may have high dislocation densities and cracks. In order to use current silicon substrates as LED-growing substrates, a solution to these issues may be required.